Interfaces & Defect Phenomena in Advanced Materials

(Supported by DOE-BES, NSF-MRSEC, SRC, Intel, NSF-MRI, ANL)

Studying structure-property relationships in advanced materials is one of the fundamental cornerstones of Materials Science and Engineering. The properties of multifunctional materials and the phenomena observed in such systems are inextricably linked to their complex interfacial and defect structures. As such, developing new materials systems and devices demands a profound understanding of the interfaces and defects in the material, whether intrinsic or engineered.

The VPD group focuses on extensively analyzing the intricate interface and defect structures in materials systems of interest by utilizing advanced electron microscopy, scanning probe and synchrotron x-ray scattering techniques. Our goal is to develop knowledge of not only static structural features, but to also monitor the dynamics of interfacial and defect phenomena using in-situ characterization techniques, and measure their localized and bulk properties. Most recently, this approach has been applied primarily to materials used for energy generation and energy storage, namely thermoelectric materials and Li-ion battery electrode materials.

Thermoelectric materials convert heat into electricity, making them a promising technology for recovering energy from waste heat. The VPD group, working with collaborators in the Kanatzidis (Chemistry) and Wolverton (MSE) groups, has shown that engineering materials with an all-scale hierarchical structure is an extremely effective approach for improving thermoelectric performance. This work, and the lessons learned, resulted in the two best thermoelectric materials to date: PbTe-SrTe and single crystal SnSe. Our current efforts are focused on developing new thermoelectric materials and studying their structural evolution at high temperature.

Understanding interface and defect structure across multiple length scales is also pivotal for developing new high-performance battery electrode materials. As members of the Center for Electrochemical Energy Science (a collaboration between ANL, UIUC, NU, and Purdue), the VPD group conducts ex-situ and also in-operando studies of model electrode materials that undergo intercalation or conversion reaction processes using Li+, Na+, and beyond. Elucidation of the structural transformations and interface dynamics within model systems aids with understanding important phenomena, such as ionic and electronic transport, and carries significant weight for correlating material structure to electrochemical performance.

In both of these fields, we make extensive use of the NUANCE center instruments and capabilities, in addition to ANL-APS synchrotron scattering facilities for both ex-situ and in-situ analysis of static and dynamic of interfacial and defect phenomena.